A hybrid electric vehicle (HEV) includes an internal combustion engine (ICE) and an electric machine that is powered by a traction battery. During a cold-start condition, the engine may be forced to run in order to bring the engine to a predetermined temperature. There may also be a demand for cabin heating during cold operating conditions, which increases the period of time that the engine runs. This mode of operation may not be the most fuel efficient and there may be lost opportunities during this time period in which the vehicle could have been operated in an electric-only mode to increase fuel economy.
Low temperatures may also affect the input and output characteristics of the high voltage battery. The battery power limits may be significantly reduced resulting in limited charging and discharging capabilities. Moreover, cold temperatures change the viscosity of the transmission oil leading to a higher parasitic viscous torque. All of these circumstances adversely affect vehicle performance and fuel economy. Accordingly, there is a need for efficient systems for warming up vehicle components during cold operating conditions that reduce engine on time and increase fuel economy.